Saturday, 15 July 2006

Arsenic Uptake of Five Vegetables from Two Natural Arsenic Contaminated Soils and One Soil Treated with Arsenic.

Majid Afyuni1, Mohammad Hajabbasi1, Mostafa Mobli1, and Rainer Schulin2. (1) Isfahan Univ of Technology, Dept of Soil Science, College of Agriculture, Iran, (2) ETHZ, Heliosstr. 11, Zurich, Switzerland

Arsenic (As) pollution of soil and drinking water has recently promoted this element into an environmental pollutant of prime concern. Arsenic toxicity is high and humans may be exposed to arsenic from a variety of environmental sources. The objectives of this study were to determine the effects of As toxicity on crop yield and uptake of As by different crops and to compare the effects between soils with a high natural As concentration and a soil that has been contaminated artificially. The study was carried out in a greenhouse using a completely randomized factorial experimental design as with four replications, using five vegetable crops (lettuce, radish, cress, bean, and spinach) that have high consumption locally and three calcareous soils. Soil 1 had a low As concentration (10 mg/kg). This soil was artificially contaminated with As at 0, 50, 150, and 250 mg As kg-1. Soils 2 and 3 naturally had 84 and 98 mg As kg-1 and no As was added to them. Arsenic concentration in roots and shoots of all the plants increased significantly with increasing As concentration on soil 1. The mean As concentration in shoots of cress, spinach, radish, lettuce and bean were 18.9, 13.4, 11.9, 10.6, and 10.5 mg kg-1 respectively, and in the roots of the crops 20.4, 17.5, 17.8, 19.1 and 8.7 mg kg-1, respectively. In general, the As concentration in the plants were higher in the soil 2 and 3 that had a high natural As concentration as compared to soil 1 that was artificially contaminated with As. This was probably due to the lower pH of soils 2 and 3 (6.4 and 6.1) compared to soil 1 (7.8). Crop yields on soil 1 deceased significantly with As treatment. At concentrations above 150 mg kg-1 all the plants showed signs of As toxicity. The results of this study shows that As can easily be taken up by vegetable crops, and at high concentrations As reduces crop yield.

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